Jumping a Rotax engine....?
There is a lot of superstition about jumping the Rotax engine with another vehicle and killing your electronics. Let's put this out there one more time.
You can jump your engine with any other 12 VDC battery, as long as the engine from that vehicle is OFF.
The idea of electrical damage comes in from the charging system of the vehicle your jumping from, having 14 VDC suppling the battery.
So, make sure the engine is off before you hook up the jumper cables.